• 한국전기전자재료학회논문지
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• 제17권1호
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• pp.31-38
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• 2004

PMN-PT, a piezoelectric single crystal, has many useful applications such as sensors and actuators. In this paper, all the elastic, piezoelectric, and dielectric constants of the PMN-32％PT single crystals were measured by the resonance method. For the rhombohedral symmetry, a total of twelve independent material constants were measured such as six elastic compliance constants at constant electric field, two dielectric constants at constant stress, and four piezoelectric constants d. Seven sets of crystal samples of each different geometry were prepared for the measurement of length-thickness extensional, thickness extensional, radial, length extensional and thickness shear modes of vibration, respectively. In order to check the validity of the measurement, experimental impedance spectrum of the PMN-PT crystal was compared with numerical data spectrum calculated with the measured material constants. The good agreement between the two spectra confirmed validity of the results in this paper.

• 한국결정성장학회지
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• 제5권1호
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• pp.11-18
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• 1995

EFG 장치를 설계제작하여 ${\Alpha} - Al_2O_3$ tube 형태의 단결정을 육성하였다. 서로 다른 두 개의 heating arrangement를 고안하여 각각의 결정 성장조건을 비교 검토하였으며, 각각의 heating arrangement에서 성장된 tube 단결정의 결함을 비교하여 안정한 성장 조건을 확립하였다.

• 한국세라믹학회지
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• 제35권3호
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• pp.280-286
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• 1998

LaAlO3 Single crystals used as a substrate for thin film depositions of a high temperature oxide su-perconductor YB2Cu3O7 and applied to microwave frequencies were grown by the Traveling Solvent Flati-ing Zone (TSFZ) method and characterized. For the growth of LaAlO3 single crystals polycrystalline fe-edrods were prepared from powder mixture of La2O3 and Al2O3 with a mole ratio of 1:1 calcined at 110$0^{\circ}C$ for 3h and sintered at 140$0^{\circ}C$ for 4h The growth LaAlO3 crystals was 4-5mm in diameter 30mm in length and dark brown. The growth rate was 2-3mm/h and the rotation speeds were 10rpm for an upper ro-tation and 40 rpm for a lower rotation The growing crystals and the feedrods were counter-rotated. The orientation of the grown single crystals of LaAlO3 was identified to be [111] direction. Dielectric constants were measured to be 30-33 between 100 kHz and 1 MHz in the 30$0^{\circ}C$ to 45$0^{\circ}C$ temperature range and 102 in a range of 100 kHz at the phase transformation temperature of 522$^{\circ}C$ Dielectric losses were calculated to be 1.8$\times$10-4 at the room temperature and 5.7$\times$10-3 at the phase transformation temperature. Lattice con-stants of the grown crystlals were determined to be aR=5.3806 $\AA$ and $\alpha$=60.043$^{\circ}$ by the least square method.

• 한국결정학회지
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• 제7권1호
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• pp.44-56
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• 1996

CuInTe2 다결정은 수평전기로에서 합성하고, CuInTe2 단결정은 수직 Bridgman 방법으로 성장하여 결정구조를 조사하고, Hall 효과를 30K에서 293K의 온도영역에서 측정하였다. CuInTe2 다결정 및 단결정은 정방정계였다. 다결정의 격자상수는 a=6.168Å, c=12.499Å 그리고 c/a=2.026이었고, 단결정의 격자상수는 a=6.186Å, c=12.453Å, 그리고 c/a=2.013이었다. CuInTe2 단결정의 성장면은 Laue 배면반사 사진으로부터 구하였으며 (112)면이었다. CuInTe2 단결정의 Hall 효과는 van der Pauw 방법으로 측정하였다. 상온에서 측정된 c축에 수직한 시료의 운반자농도 p는 2.14×1023holes/m3, 전기전도도 δ는 739.58Ω-1m-1 그리고 이동도 μ는 2.16×10 m2/V·s 이었다. c축에 평행한 시료의 운반자농도 p는 1.51×1023holes/m3, 전기전도도 σ는 717.55Ω-1m-1 그리고 이동도 μ는 2.97×10-2 m2/V·s이었다. c축에 수직 및 평행한 시료의 Hall계수가 양의 값이어서 CuInTe2 단결정은 p형 반도체임을 알 수 있었다.

• 한국재료학회지
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• 제12권11호
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• pp.875-879
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• 2002

$Pb_{1-x}$ $Cd_{x}$ $I_2$ (x=0.0, 0.2, 0.5, 0.7, 0.9, 1.0) single crystals were grown by using Bridgman method and their structural and optical properties were investigated from the measurement of X-ray diffraction, optical absorption and photoluminescence. As-grown single crystals have hexagonal closed packed layered structure. The values of lattice constant c decrease with increasing composition x. Direct and indirect transition optical energy band gaps are calculated from optical absorption spectra measured at room temperature. They increase exponentially from 2.3eV to 3.2 eV with increasing composition x. The energies of photoluminescence peak due to donor bound exciton measured at 6K increase with increasing composition . However, the peak energies of donor-acceptor pair (DAP) are independent of the optical energy band gaps of $Pb_{1-x}$/$Cd_{x}$ $I_2$ single crystals.

• 한국재료학회지
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• 제15권3호
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• pp.195-201
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• 2005

The $SnS_2,\;SnS_2:Cd$, and $SnS_2:Sb$ single crystals were grown by the chemical transport reaction method. The indirect optical energy band gap was found to be 2.348, 2.345, and 2.343 eV for the $SnS_2,\;SnS_2:Cd$, and $SnS_2:Sb$ single crystals, at 6 K respectively. The direct optical energy band gap was found to be 2.511, 2.505, and 2.503 eV f3r the $SnS_2,\;SnS_2:Cd$, and $SnS_2:Sb$ single crystals, at 6 K respectively The temperature dependence of the optical energy band gap was well fitted by the Varshni equation. Two photoluminescence emission peaks with the peak energy of 2.214 and 1.792 eV for $SnS_2$, 2.214 and 1.837 eV for $SnS_2:Cd$, and 2.214 and 1.818 eV the $SnS_2:Sb$ were observed. The emission peaks were described as originating from the donor-acceptor pair recombinations.

• Progress in Superconductivity
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• 제11권2호
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• pp.118-122
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• 2010

Electrical transport properties were measured on $SmFeAsO_{0.85}$ single crystals along the c-axis for various temperatures and magnetic fields. For the measurements a mesa structure was fabricated on the surface of the single crystals. Samples showed a metallic temperature dependence of resistance and current-voltage curves without hysteretic multiple branch splitting that is usually observed in tunneling Josephson junctions. In addition, in ab-planar magnetic fields, samples did not show the Fraunhofer-type field modulation of the critical current. All these features indicate that the c-axis transport characteristics of $SmFeAsO_{0.85}$ single crystals are explained by the anisotropic bulk superconductivity rather than Josephson tunneling.

• 한국광물학회지
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• 제10권1호
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• pp.18-32
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• 1997

Analysis of geological data, relating to occurrence and formation of diamonds as well as host rocks, inclined author to have different outlook on the diamond genesis and to establish a proposition on their formation at pneumatolytic-hydrothermal conditions near superficial Earth zones. Based on that theoretical foundations and experimental works, the first low-pressure and low-temperature hydrothermal diamond synthesis from water solution in pressure autoclave was executed. As a result, the natural diamond seed crystal grew bigger ad coupling of the synthetic diamond single-crystalline grains were obtained. SEM documentation proofs that parallely paragenetic crystallization of quartz and diamond, and nucleation of new octahedral diamond crystals brush take place on the seed crystal surface. Forecast of none times growth of diamond industrial application at 2000 and seventeen times at 2010 with reference to 1995, needs technology of large and pure single-crystals diamond synthesis. Growth of the stable and destressed diamond single-crystals in the pseudo-metastable diamond plot, may be realized with processes going through the long time and with participation of free radicals catalysts admixtures only. Sol-gel colloidal processes are an example of environment which form stable crystals in thermodynamically unstable conditions through a long time. Paper critically discusses a whole way of studies on the diamond synthesis, from high-pressure and high-temperature processes through chemical vapour deposition up to hydrothermal experiments.

• 한국결정학회:학술대회논문집
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• 한국결정학회 2003년도 춘계학술연구발표회
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• pp.19-19
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• 2003

A cubic perovskite-type CaCu₃Ti₄O/sub 12/ compound has recently drawn a great attention because of an extraordinary high permittivity (～10⁴ at 1 kHz) at room temperature and its near temperature-independence over a wide temperature region, and thus numerous literature have been reported on CCTO polycrytalline ceramics and thin films. However, only a few literature have been reported on the CCTO single due to the lack of information about the CCTO primary phase field. On the basis of our recent experimental determination of the CCTO primary phase field, we could grow ACu₃Ti₄O/sub 12/(A=Ca, Sr) single crystals using both top-seeded solution growth and flux growth methods. This presentation will include three major parts. In part I, the thermal decomposition reaction of CCTO and its primary phase field in the CaO-CuO-TiO₂ ternary system will be presented. Detailed growth conditions of ACu₃Ti₄O/sub 12/(A=Ca, Sr) single crystals and characteristics of as-grown crystals will be followed in Part II. Part III will be comprised of dielectric properties of as-grown ACu₃Ti₄O/sub 12/(A=Ca, Sr) single crystals. Our experimental results will be compared with those of previous reports for discussion.

• 한국전기전자재료학회논문지
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• 제34권6호
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• pp.466-474
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• 2021

[011] poled ternary Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PMN-PT) single crystals have been investigated for active materials for acoustic transducers because of their high piezoelectric properties in both shear and transverse modes. In order to use [011] poled PIN-PMN-PT single crystals for acoustic transducers, the characterization of full-matrix material properties is required. In this study, full sets of compliance, dielectric, and piezoelectric constants of [011] poled rhombohedral PIN-PMN-PT were measured by a resonance method. Dimensions and geometries of 12 samples were proposed for measuring 17 independent material constants of [011] poled rhombohedral PIN-PMN-PT single crystals. Two sets of samples with different PT concentrations, 0.24PIN-0.49PMN-0.27PT and 0.24PIN-0.46PMN-0.30PT, were fabricated and their material properties were measured. Measured impedance spectra and simulated impedance spectra of the samples were compared to check the accuracy of the measurements.